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We report here the first direct observation of U(V) in uranium binary oxides and analyze the gradual conversion of the U oxidation state in the mixed uranium systems. Our finding clarifies previous contradicting results and provides important input for the geological disposal of spent fuel, recycling applications, and chemistry of uranium species. [ABSTRACT FROM AUTHOR]

The article describes the structure of the Ce L3 x-ray absorption spectra (XAS) of CeFe2. The single impurity Anderson model (SIAM) and the first-principles band calculations based on the density-functional theory (DFT) were utilized to describe the structure. It was discovered that the mixed valence 4f character revealed by the core-hole potential effect influence the structure of Ce L3 XAS.

We present resonant x-ray emission spectroscopic data from the uranium intermetallics UPd3, USb, USn3, and URu2Si2 at the M4,5 edges of uranium, and we compare the data to those from the well-localized 5f² semiconductor UO2. The technique is especially sensitive to any oxidation of the surface, and this was found on the USb sample, thus preventing a good comparison with a material known to be 5f³. We have found a small energy shift between UO2 and UPd3, both known to have localized 5f² configurations, which we ascribe to the effect of conduction electrons in UPd3. The spectra from UPd3 and URu2Si2 are similar, strongly suggesting a predominant 5f² configuration for URu2Si2. The valence-band resonant inelastic x-ray scattering provides information on the U P3 transitions (at about 18 eV) between the U 5f and U 6p states, as well as transitions of between 3 and 7 eV from the valence band into the unoccupied 5f states. These transitions are primarily involving mixed ligand states (O 2p or Pd,Ru 4d) and U 5f states. Calculations are able to reproduce both of these low-energy transitions reasonably well. [ABSTRACT FROM AUTHOR]

We resolved a recent controversy on the structure of the Ce L(3) x-ray absorption spectra (XAS) of CeFe(2); i.e., which of the single impurity Anderson model (SIAM) and the first-principles band calculations based on the density-functional theory (DFT) describes more appropriately the Ce 4f states and their contribution to the Ce L(3) XAS? For this purpose, we examined the core-hole effect in Ce L(3) XAS as an application of our new method taking advantage of resonant x-ray emission spectroscopy. Our result clearly shows that the Ce L(3) XAS structure is caused by the mixed valence 4f character revealed by the core-hole potential effect as indicated by SIAM, but denies the possibility that the L(3) XAS structure is caused by the 5d band structure with a very small core-hole effect as predicted by band calculations based on DFT., (© 2012 American Physical Society)